Composition with a time release material for removing halogenated hydrocarbons from contaminated environments

ABSTRACT

A composition for remediation of soil and groundwater containing halogenated compounds. The remediation composition includes an elemental iron-based composition, which may include activated carbon capable of absorbing the halogenated compounds with numerous pores impregnated with elemental iron. The remediation composition further includes a first bioremediation material including a blend of one-to-many organisms capable of degrading the halogenated compounds. The remediation composition includes an organic compound or polymeric substance and a second bioremediation material including a blend of one-to-many organisms capable of degrading the organic compound or polymeric substance over time (e.g., 20 to 365 or more days to provide a time release substrate-creating material or platform) into smaller molecules or compounds used by the organisms in the first bioremediation material while degrading the halogenated compounds. The organic compound may be a complex carbohydrate such as food grade starch, chitin, or other complex carbohydrate such as one with low water solubility.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/686,561, filed Nov. 18, 2019, which is a continuation-in-part of U.S.patent application Ser. No. 15/147,733, filed May 5, 2016, both of whichare incorporated herein in their entireties.

BACKGROUND OF THE DESCRIPTION 1. Field of the Description

The present invention relates to compositions and methods for in situremediation of contaminated environments, and particularly to theremediation of soil and/or groundwater contaminated with halogenatedhydrocarbons.

2. Description of the Related Art

With increased concerns over protecting the environment and publichealth and safety, the identification and removal of contaminantmaterials in the environment, and especially from the groundwatersupply, has become one of the most important environmental concernstoday. Years of unregulated dumping of hazardous materials have severelycontaminated the groundwater in many areas, creating significant healthconcerns and causing extensive damage to the local ecosystem. As aresult, in recent years significant emphasis has been placed upon theclean-up and remediation of contaminated groundwater and the environmentsurrounding dump sites, which has led to the creation of a new industryof environmental clean-up and remediation. However, conventionaltechnologies currently being used for remediation for contaminated sitesoften are very expensive, can require years to perform, and are notalways effective.

Because of the widespread use of both chlorinated solvents and petroleumhydrocarbons, contaminated ground water has been found in many sitesaround the world. Chlorinated solvents, such as trichloroethane (TCE)and perchloroethylene (PCE), are used for such purposes as dry cleaning,and as degreasers and cleaners in a variety of industries. Petroleumhydrocarbons commonly found in ground water include the components ofgasoline, such as benzene, toluene, ethylbenzene, and xylene. Anothercommon contaminant of ground water is naphthalene. Additionalgroundwater and soil contaminants include polycyclic aromatichydrocarbons (PAHs) created from combustion, coal coking, petroleumrefining and wood-treating operations; and polychlorinated biphenyls(PCBs), once widely used in electrical transformers and capacitors andfor a variety of other industrial purposes, pesticides, and herbicides.

Various ex situ and in situ methods have been utilized for thetreatment, remediation, and disposal of contaminated soil. Ex situmethods generally include permanent removal of the contaminated soil toa secure landfill, incineration, indirect thermal treatment, aeration,and venting. Removal of contaminated soil to landfills is no longer anattractive alternative because of the high excavation, transportation,and disposal costs and because of the potential for residual liability.Incineration and indirect thermal treatment can be achieved eitheron-site or off-site but, in either case, involves excavation, handling,and treatment of substantially all the contaminated soil as well assignificant amounts of soil adjacent to the contaminated soil. The soilmust then either be transported to the treatment facility or else thetreatment apparatus must be installed on-site. Other elaborate andexpensive techniques that have been utilized involve excavation andtreatment of the contaminated soil using multistep unit operations forseparating and recovering the soil from the contaminants.

Additional existing clean-up methods and technologies include “pump andtreat” methods in which contaminated groundwater is pumped to thesurface, cleaned chemically or by passing the groundwater through abioreactor, and then reinjected into the groundwater. Such a processgenerally is carried out over a long period of time, typically one toten years or more. A common remediation treatment for ground watercontaminated with chlorinated hydrocarbons involves pumping the waterout of the well or aquifer, volatizing the contaminants in an airstripping tower, and returning the decontaminated water to the groundsite. A related type of environmental remediation is the “dig and haul”method in which contaminated soils are removed and then treated or landfilled.

The biggest problem with pump and treat systems is that, over time, theybecome more and more inefficient, so that stable residual concentrationsbecome established. When this happens, the system is said to be“flat-lined” and very little further benefit is obtained. In addition,channeling often occurs so that large pockets of contamination are leftbehind, and rebound frequently occurs after the pumps are turned off.

A wide variety of materials and methods have been evaluated for in situremediation of chlorinated hydrocarbons, including zero valent iron(ZVI), potassium permanganate, and hydrogen peroxide. ZVI renders thechlorinated hydrocarbon less toxic by reductive dehalogenation, i.e., byreplacement of chlorine substituents with hydrogen. In this method,reactive walls are constructed by digging a trench across the plumemigration path and filling it with iron filings. Sheet piling or someother means of directing the flow of groundwater is used to directcontaminated groundwater through the filing wall. The chlorinatedhydrocarbons react with the elemental iron as the groundwater flowsthrough the wall, and ideally, clean water emerges on the down gradientside of the wall. The disadvantage of the wall method lies in thedifficulty of introducing large volumes of solid reactive material, suchas iron particles, at effective depths. Conventional excavation methodsgenerally limit the practical working depth to about 30 feet, whereasground water contaminants are found at depths as great as 300 feet.Also, there may be a reduced permeability in the wall over time due toprecipitation and plugging. Further, the reactive wall approach may notbe useful in degrading methylene chloride and may be very slow (e.g.,taking up to 10 or more years to achieve any substantial remediation).

Oxygen release materials (ORMs) are compositions such as intercalatedmagnesium peroxide that release oxygen slowly and facilitate the aerobicdegradation of hydrocarbon contaminants in situ. ORMs are most effectivewhen used to polish up after a mechanical system has flat-lined and areleast effective at new sites where no other remedial measures had beenimplemented. They are disadvantaged in that ORMs are expensive, andlarge amounts are required for complete oxidation. Additionally,multiple treatments are often required in order to achieve targetedcleanup goals, and up to five years may be needed to complete theprocess.

Hydrogen Release Compound® (HRC) is an alternative option for the insitu remediation of chlorinated hydrocarbons under anaerobic conditionsvia reductive dehalogenation. When in contact with subsurface moisture,HRC® is hydrolyzed, slowly releasing lactic acid. Indigenous anaerobicmicrobes (such as acetogens) metabolize the lactic acid producingconsistent low concentrations of dissolved hydrogen. The resultinghydrogen is then used by other subsurface microbes (reductivedehalogenators) to strip the solvent molecules of their chlorine atomsand allow for further biological degradation. HRC® is injected into theaffected environment under pressure and each treatment lasts for roughlysix to nine months. Like ORMs, HRC® is expensive, and large amounts arerequired for complete degradation. Additionally, multiple treatments arealways required in order to achieve targeted cleanup goals, and up tofive years may be needed to complete the process.

Another emerging clean-up technology is “bioremediation,” in whichnatural or genetically engineered microorganisms are applied tocontaminated sites such as groundwater, soils or rocks. In thistechnique, specialized strains of bacteria are developed that metabolizevarious hydrocarbons such as gasoline, crude oil, or otherhydrocarbon-based contaminates and gradually reduce them to carbondioxide and water. However, such bacterial remediation requires that thebacteria and the hydrocarbon be brought into intimate contact underconditions in which the bacteria will act to metabolize thehydrocarbons. This requires extensive labor and effort to spread thebacteria on the soil and then to continually work and rework thecontaminated area, turning and tilling the soil, until such time as thebacteria have been brought substantially into contact with all thecontaminated hydrocarbon particles. An additional drawback has been theineffective spreading of injected bacteria due to clogging around thewells due to adsorption and growth of the bacteria about the wells.

The above-described technologies share one or more of the followingdrawbacks: (1) long periods of time are required for sustained reductionin contaminant concentrations to be realized; (2) although reductionscan be realized, regulatory cleanup standards or goals for soil andgroundwater are seldom attained; (3) performance is inconsistent andhighly dependent on site conditions and contaminant levels; (4) withrespect to active systems, contaminants are often removed from oneformation (groundwater for example) and then released into another, suchas air, and as a result, contaminants are not destroyed, just moved fromone place to another; and (5) with respect to passive systems fortreatment of chlorinated solvents, by-products are often released thatare more toxic than the original contaminants, creating a transientcondition more egregious than what existed before treatment.

Hence, a need remains for remediation processes to effectively clean upsoil and/or groundwater contaminated with hydrocarbons and/orhalogenated hydrocarbons that is rapid, cost effective, and does notrelease toxic by-products into the soil, air or groundwater.

SUMMARY

The present description provides compositions and methods for in situsoil and/or groundwater remediation that can reduce contaminantconcentrations quickly to regulatory cleanup standards. The compositionsand methods work in a variety of soil and groundwater conditions and areapplicable for the remediation of a variety of contaminants. The methodsand compositions of this description do not release toxic by-productsinto the soil, groundwater, or air and have no impact on soil propertiesor groundwater quality. The compositions of this description are alsocost effective in that they remain active for an extended period of timeso that only a single treatment is required.

In prior work, the inventor created a composition which, when added to asite such as soil and/or groundwater contaminated with one or morehalogenated hydrocarbons, adsorbs the halogenated hydrocarbons, andreduces them to less innocuous by-products. This composition was agranular activated carbon whose inner pore structure had beenimpregnated with elemental iron. This elemental iron-based compositionmay be considered a supported reactant for in situ remediation of soiland/or groundwater contaminated with one or more halogenatedhydrocarbon. The supported reactant was formed mainly of an adsorbentimpregnated with zero valent iron, and the adsorbent is chosen to becapable of adsorbing the halogenated hydrocarbon contaminants as well asthe intermediate by-products resulting from the degradation of thecontaminants. In one embodiment, the adsorbent is activated carbon. Theinventor determined that this elemental iron-based composition wasuseful in methods for the remediation of an environment contaminatedwith halogenated hydrocarbons, with such methods including adding thesupported reactant to one or more sites of the contaminated environment.In this manner, reductive dehalogenation of the halogenated hydrocarboncontaminants is achieved.

Regarding the present description, though, the inventor furtherrecognized there may be a useful synergy between this elementaliron-based composition and bioremediation technologies. Particularly, itwas understood that successful degradation of halogenated hydrocarbonsor other contaminants is often mainly about achieving successfulelectron transfer. To this end, the elemental iron-based composition maybe used with a first blend of organisms that are chosen for theirability to degrade chlorinated solvents and other halogenated compounds.For example, the elemental iron-based composition may act to absorb thecontaminants within the pores of the activated carbon near theimpregnated iron, which acts in conjunction with this first blend oforganisms to degrade the contaminants.

Further, though, the inventor recognized that it is desirable to “feed”or “fuel” the organisms of the first blend/composition to continue todegrade the contaminants over a longer period of time. Prior substratesused for this purpose often were ineffective as they donate hydrogen orthe like very quickly and do not continue to be effective in feeding orfueling the first blend of organisms over time (e.g., over 20 to 40 daysor more).

To this end, the inventor discovered that it would be useful to providea combination of an organic compound (or polymeric substance or polymer)such as a complex carbohydrate to fuel/feed the first blend of organismsand a second blend of organisms whose sole purpose/function is to breakthe organic compound(s) into smaller molecules that are more readilyutilized by the microorganisms of the first blend to support degradationof the contaminants. In this way, the fuel or smaller molecules from thesubstrate are made available in a time released manner (e.g., theorganic compound with the organisms acts as a time release material)that facilitates the degradation of the contaminants over a much longerperiod of time so as to achieve greater percentages of degradation(e.g., 64 to 86 percent degradation achieved in some bench trials). Inparticular implementations, the organic compound is a complexcarbohydrate that is (or includes) starch (such as a food grade starchfrom a source such as corn, starch, rice, wheat, or the like) whileother exemplary, but not limiting, implementations utilize chitin.

More particularly, a composition is provided that is particularly wellsuited for remediation of soil, wastewater, or groundwater containinghalogenated compounds (such as halogenated fuels, chlorinated solvents,and the like). The remediation composition includes an elementaliron-based composition, and a first bioremediation material including atleast one microorganism (and typically a blend of many microorganismssuch as unicellular organisms or bugs such as bacteria, archaea, and thelike and also including fungi and other organisms as taught herein)capable of degrading halogenated compounds. Significantly, theremediation composition further includes an organic compound orpolymeric substance (or polymer) such as a polysaccharide (e.g., acomplex carbohydrate (such as a food grade starch)) and a secondbioremediation material including at least one organism (and typically ablend of many microorganisms) capable of degrading the complexcarbohydrate. The remediation composition is a “time release material”because degrading of the organic compound or polymeric substance (e.g.,a complex carbohydrate such as starch, chitin, or the like) by theorganisms of the second bioremediation material is performed over a timeperiod of at least 20 days such as 365 or more days (e.g., the timerelease functionality may extend over one to three or more years in somecases).

In some useful embodiments, the organic compound includes a complexcarbohydrate in the form of a starch (e.g., a food grade starch such ascorn, wheat, rice, tapioca, potato (including sweet potato), sago, mungbean, or arrowroot starch or a blend of such starches) while otherremediation compositions utilize chitin. In practice, degrading of theorganic compound or polymeric substance by the at least one organism ofthe second bioremediation material comprises breaking the organiccompound into a plurality of smaller molecules utilized (e.g., aselectron donors) by the at least one organism of the firstbioremediation material during the degrading of the halogenatedcompounds.

The remediation composition may be effectively implemented in oneembodiment when the elemental iron-based composition includes activatedcarbon with pores impregnated with zero valent iron (ZVI). In the sameor other implementations, the elemental iron-based composition mayinclude activated carbon that is capable of adsorbing the halogenatedcompounds and that has numerous pores impregnated with iron. In somepreferred embodiments, the iron (or elemental iron particles) isimpregnated into the activated carbon by being at least partiallydissolved into walls of the pores, and transitions between the activatedcarbon and the iron include cast iron and iron carbide, which may makethe elemental iron-based composition much more effective at degradinghalogenated compounds.

In some embodiments, the elemental iron-based composition has betweenabout 1 and 20 percent by weight of the iron. In these or otherembodiments, the exposed surface area of the iron is between about 50and 400 m²/g. Further, it may be desirable for the activated carbon tohave a surface area between about 800 and 2000 m²/g.

DETAILED DESCRIPTION

The following description relates to new remediation compositions andmethods for in situ remediation of environments such as soil orgroundwater contaminated with halogenated hydrocarbons. The descriptionbuilds upon prior discoveries made by the inventor of a supportedreactant (or elemental iron-based composition) that is particularly wellsuited for cleaning up soil and groundwater contaminated withhalogenated hydrocarbons. The effectiveness of this supportedreactant/elemental iron-based composition is greatly enhanced, though,by combining it with bioremediation technologies (e.g., a set or blendof one-to-many microorganisms) suited for degrading halogenatedhydrocarbons to create a new remediation composition.

Further, the effectiveness of the bioremediation technologies isincreased by including in the new remediation composition a combinationof a time release material (or organic compound or polymeric substance(such as a complex carbohydrate (e.g., starch, chitin, or the like))with a second set or blend of one or more microorganisms chosen forbreaking up or degrading the time release material (e.g., a complexcarbohydrate) into smaller molecules for better utilization over time bythe second set or blend of microorganisms. Stated differently, theelemental iron-based composition (or supported reactant as calledherein) combined with the organic compound(s) or polymeric substance(s)(e.g., a starch (or other complex carbohydrate) and microorganismsdegrading organic compounds/polymeric substances provide a time releasecomposition or platform that acts to enhance and support (e.g., fuel)the degradation over a relatively long period (e.g., 20 to 365 days ormore). This time release platform is used (as it slowly releaseshydrogen or the like) in the new composition described herein by the setor blend of microorganisms included that degrade the contaminants suchas halogenated hydrocarbons.

With regard to “the time release material” to be used, the inventorunderstood that polymers are large molecules formed when monomers linktogether to form the larger molecule. The monomer can be a simplecompound like ethylene (CH₂CH₂) or a more complex substance or materialsuch as a sugar. In general, polymers have the following structure:[repeating unit]n, where the repeating unit is a monomer and n is thedegree of polymerization. With respect to degradation of halogenatedorganic compounds, many simple substances have been used to promote suchdegradation. However, they are typically very short lived and includesugars and fatty acids like lactic acid. As previously described, thesesimple substances or compounds are water soluble and readily consumed bya variety of microorganisms.

Hence, the inventor recognized the need for a time release material thatwould be a source of such compounds that play the role of a substratethat can be beneficially used by organisms capable of degradinghalogenated compounds. Specifically, the inventor discovered thatorganic compounds or polymeric substances (or polymers) were goodsources of such time released materials. Naturally occurring polymersmay be preferred in some applications, but manmade polymers may also beused to practice remediation products/processes of the presentdescription.

Naturally occurring polymers fall into three general types orcategories: (1) polynucleotides; (2) polyamides; and (3)polysaccharides. Of these, the inventor discovered that polyamides andpolysaccharides are likely the most applicable and useful. In somespecific embodiments, one of the more effective polymeric substances ororganic compounds presented in this description are complexcarbohydrates such as one or more starches (which are polysaccharides).Polymers contain monomeric units that can fulfill the role of a timerelease material, which is beneficially used to support degradation ofhalogenated compounds. Polymeric fatty acids such as polylactic acid andpolymers of amino acids (polyamides) are additional examples of organiccompounds or polymeric substances that may be utilized. Short chains ofamino acids with 6 to 30 acids linked together by peptide bonds arereferred to as polypeptides. When the number of amino acids reaches 40or more (molecular weight of 5000 Da (Daltons)), the chain takes on theproperties associated with proteins. Examples of proteins that may beused in the remediation compositions include casein, yeast extract, andpeptone.

In general, polymeric substances that can be used as part of theremediation compositions described and claimed herein include organiccompounds, which typically will include monomeric units that can be usedas a time release material supporting the degradation of halogenatedorganic compounds with average molecular weight exceeding 2500 Da ormore preferably exceeding 5000 Da. Polysaccharides may alternatively becharacterized according to the general formula C_(x)(H₂O)_(y), where xis an integer greater than 12 and preferably where x is an integerbetween 200 and 2500 and further where x and y are different integers.Alternatively, polysaccharides may be characterized according to thegeneral formula (C₆H₁₀O₅)_(n), where n is an integer that, in oneembodiment, is greater than or equal to 40 and less than or equal to3000.

The following description provides specific examples of polymericsubstances and/or organic compounds in the form of complex carbohydratessuch as food grade starch. However, it will be understood by thoseskilled in the art that these are non-limiting examples and otherorganic compounds or polymeric substances may be substituted in theseremediation compositions. The description also discusses the supportedreactant or elemental iron-based composition that is included in the newremediation composition and how it may be manufactured. The descriptionprovides a method of using the new remediation composition todecontaminate soil and/or groundwater. The description then proceeds todetail possible mixtures or “recipes” for providing or manufacturing thenew remediation composition.

More specifically, the remediation composition may include a supportedreactant for the reductive dehalogenation of halogenated hydrocarbons.The reactant may consist essentially of an adsorbent impregnated withzero valent iron, and the adsorbent may have an affinity for halogenatedhydrocarbons. In addition, the adsorbent can be chosen so as to becapable of adsorbing toxic intermediate by-products produced by thereductive dehalogenation of the contaminants, e.g., intermediates suchas dichloroethane and intermediate by-products of trichloroethanedecomposition. In this way, the adsorbent provides a means forconcentrating contaminants into a new matrix where a high surface areaof iron is available, as discussed hereinafter in detail. The supportedreactants accomplish treatment of halogenated hydrocarbons in soil andgroundwater, at least in part, by degrading halogenated hydrocarboncontaminants and their toxic intermediate by-products into harmlessby-products (e.g., ethane, ethene, etc.).

The supported reactants are in some implementations prepared using anadsorbent having a high surface area per unit weight and a high affinityfor halogenated hydrocarbons. Suitable adsorbents for these purposesinclude, but are not limited to, activated carbon, vermiculite, alumina,zeolites, and chars such as wood, bone, and the like. Thus, while themethod of preparing the supported reactants is described utilizingactivated carbon as the adsorbent, it is to be understood that themethods and supported reactants that may be used in the new remediationcomposition are not limited to only this adsorbent.

In one non-limiting embodiment, the supported reactant consistsessentially of activated carbon as the support, and the activated carbonis impregnated with zero valent iron. The activated carbon preferablyhas a high surface area per unit weight (preferably ranging from 800 to2000 m²/g) and a high affinity for halogenated hydrocarbons. The abilityof activated carbon to adsorb organics from water enhances its utilityas a support. However, while the activated carbon can trap hydrocarboncontaminants, carbon by itself is not stable over long periods, i.e., itis subject to erosion, in which case the contaminants move with theactivated carbon and are not truly trapped and removed. Activated carbonprovides an efficient matrix for adsorption of the chlorinatedhydrocarbon contaminants. Impregnating the activated carbon with thezero valent iron provides sub-micron deposits of iron within the porestructure of the carbon, thus maximizing the metal's available surfacearea and placing the metal where the concentration of adsorbedcontaminant molecules is the highest. Accordingly, the supportedreactant allows efficient contact of the iron with adsorbed chemicalscontaminants, since the iron will be in close proximity to thecontaminant. The supported reactants of the new remediation compositionaccomplish treatment of chlorinated hydrocarbons in soil and groundwaterby degrading these chemicals into harmless by-products.

Activated carbons can be manufactured from a broad spectrum of materialincluding, but not limited to, coal, coconut shells, peat, and wood. Theraw material is typically crushed, screened, and washed to removemineral constituents. The material is then activated at hightemperatures (typically over 900° C.) in a controlled atmosphere toproduce a material having an extensive porous network and a largesurface area (e.g., ranging from 1000 to 2000 m²/g). The supportedreactants may be produced with virtually any source of activated carbon.All that is needed are minor adjustments in system design parameters toaccount for the different forms of carbon. When the product is used forremediation of groundwater, acid-washed carbons may be useful since theacid wash removes any extraneous metals that may be of environmentalconcern from the carbon.

With activated carbon, available surface areas for adsorption preferablyrange from about 800 m²/gm to 2000 m²/gm. Some loss of carbon surfacearea may occur during the impregnation process, but testing has shownthat the loss is not significant when measured by adsorption isotherms.In one embodiment, the surface area of the zero valent iron used in thesupported reactant included in the remediation composition ranges fromabout 50 to 400 m²/(gm-deposited iron). The weight percent of irondeposited within the carbon matrix ranges from about 1 percent to 20percent by weight of iron and, in some useful embodiments, in the rangeof about 7 to 8 percent by weight of iron. In one embodiment, thesupported reactant has a total surface area of over 1500 m²/g. The ironcontained in the supported reactants typically is a high purity iron. Inother words, the iron does not contain other metals, such as heavymetals, which would contaminate groundwater and drinking water beyondlimits allowed by the EPA. Preferably, the iron is at least 99% pure,and the concentrations of trace contaminants such as chromium, aluminum,potassium, cesium, zinc, lead, nickel, cadmium, and/or arsenic are lessthan 5 ppm. In some cases, the source of the iron is a food grade salt.

In one particular embodiment, a supported reactant used in theremediation composition for in situ remediation of soil and/orgroundwater contaminated with a halogenated hydrocarbon, includes (oreven consists essentially of in some cases): (i) an adsorbentimpregnated with zero valent iron and (ii) a metal hydroxide or a metalcarbonate (such as limestone) in an amount sufficient to provide areactant having a pH greater than 7. The adsorbent is selected to becapable of adsorbing the halogenated hydrocarbon. Suitable adsorbentsfor purposes of this invention include, but are not limited to,activated carbon, vermiculite, alumina, and zeolites.

As described above, the contaminants in the soil/ground water beingremediated are initially adsorbed by the activated carbon and thendegraded through a reductive dechlorination mechanism. However, toxicreaction by-products such as vinyl chloride and cis-dichloroethene maybe formed during the treatment process. In conventional remediationsystems, even though these by-products will react with the iron, they doso at a reduced rate and concentrations can initially rise. In fact,fairly large accumulations can occur, creating a more acute risk to theenvironment than that which originally existed. One of the advantages ofthe supported reactant described herein for use in the remediationcomposition is that these toxic by-products are also readily adsorbed bythe activated carbon. As a result, little if any by-product escapes fromthe carbon matrix and groundwater quality is protected throughout thecleanup lifecycle. Further, the supported reactant degrades theintermediate by-products into non-toxic by-products such as ethane,ethene, and ethyne.

Manufacture of the supported reactant may involve methods that producean adsorbent (e.g., activated carbon) impregnated with zero valent iron,which can be achieved using a variety of procedures known to thoseskilled in the art. A first exemplary method of producing a supportedreactant involves mixing the adsorbent with a calculated amount of ahydrated iron salt such as ferric nitrate while warming to melt thehydrated iron salt. The iron can be an iron (II) or an iron (III) salt.The mixture is dried and pyrolyzed to decompose the iron salt to ironoxide, forming an intermediate product (i.e., the activated carbonimpregnated with a form of iron oxide). The intermediate product is thensubjected to reduction conditions to reduce the iron oxide to elementaliron, thereby producing the activated carbon impregnated with elementaliron.

A second exemplary method for preparing a supported reactant involves aslow precipitation of goethite (iron hydrogen oxide) from a solution ofan iron salt (e.g., ferrous sulfate) by addition of a dilute sodiumbicarbonate solution. The precipitation is carried out with vigorousmixing in a suspension of the activated carbon to provide anintermediate product (i.e., the adsorbent impregnated with a form ofiron oxide). This intermediate product is then washed, dried, andfinally reduced to convert the iron oxides to elemental iron, therebyproducing the activated carbon impregnated with elemental iron.

A third exemplary method of preparing a supported reactant involvestreatment of the activated carbon with a solution of a water solubleiron salt, such as iron (II/III) sulfate, iron chloride, iron citrate,iron nitrate, or any other suitable water soluble iron salt. Thesolution can be sprayed onto the carbon or the carbon may be suspendedin a measured volume of the iron salt solution sufficient to achieve thedesired loading. The suspension is then de-aerated by applied vacuum.Depending on the chosen process for final reduction, the saltimpregnated material can be dried and reduced directly, orneutralization of the salt may be provided by the addition of a dilutesodium bicarbonate or sodium hydroxide solution over a period of time,thereby producing iron oxides/hydroxide within the carbon. In the lattercase, the iron oxide or iron hydroxide-impregnated activated carbon isthen subjected to reducing conditions to reduce the iron oxide or ironhydroxide to zero-valent iron.

In one embodiment, the effectiveness of the supported reactant isenhanced by increasing the pH of the supported reactant to a basic pH,such as by adding a small percentage of magnesium hydroxide (or othermetal hydroxide or, in some cases, a metal carbonate (such aslimestone)) to the supported reactant to raise the pH above 7.0.

The remediation composition that includes these supported reactants(along with blend or set of one or more organisms for bioremediation, acomplex carbohydrate, and a blend or set of organisms for degrading thecomplex carbohydrate) can be applied to treatment of water contaminatedwith a variety of water miscible or soluble halogenated organiccompounds. Chlorinated solvents are particularly common contaminants inaquifers and other subsurface water-containing environments.Contaminants that may be effectively treated include halogenatedsolvents such as, but not limited to, (TCE), dichloroethylene (DCE),tetrachloroethylene, dichloroethane, vinyl chloride (VC), chloroethane,carbon tetrachloride, chloroform, dichloromethane and methyl chloride.Other classes of contaminants that may be effectively treated includebrominated methanes, brominated ethanes, brominated ethenes,fluorochloromethanes, fluorochloroethanes, fluorochloroethenes,polychlorinated biphenyls (PCBs), and pesticides.

In this regard, the description provides a method of remediating a sitecontaminated with halogenated hydrocarbons. The method includesinjecting a remediation composition with a supported reactant of thisdescription into one or more locations of the contaminated site.Illustrative examples of contaminated environments that can be treatedwith the remediation composition with a supported reactant combined withbioremediation organisms (and a starch or other complex carbohydrate anddegrading organisms) include, but are not limited to, soil, sediment,sand, gravel, groundwater, aquifer material, and landfills. For example,in one embodiment, the remediation composition with supported reactantis injected into multiple sites within an aquifer, as described inExample 3. In this embodiment, the application method results in asubstantially homogeneous distribution of the remediation compositionwith supported reactant in the contaminant plume, as opposed to creatinga barrier or filled trench as in conventional methods. Thus, theremediation method according to the embodiment described in Example 3using a remediation composition with supported reactant does not rely ongroundwater advection for effective treatment. Rather, the activatedcarbon component of the supported reactant of the remediationcomposition concentrates the contaminants within the adsorbent matrixwhere a high surface area of iron is available, thereby increasing therate of contaminant degradation. Contaminated ground water in the sitesubsequently contacts the supported reactant, whereby reductivedehalogenation of the halogenated hydrocarbon compounds is achieved incombination with the blend or set of organisms included for degradinghalogenated compounds.

The supported reactant provides a number of advantages over conventionalremediation products and methods. For example, it rapidly reducesconcentrations of contaminants in groundwater so that regulatorystandards can be approached or achieved in a short time frame (e.g.,within several days or a few weeks, versus several months or years withconventional methods). In addition, the supported reactant is non-toxic,does not decompose over time, and toxic degradation by-products are notreleased, so groundwater quality is protected throughout treatment. Thesupported reactant has the ability to treat a variety of chlorinatedchemicals and is effective in all types of soil and groundwaterconditions. It remains active for an extended period of time so thattypically only a single treatment is required. This “time release”characteristic is effectively paired with the time releasecharacteristics of the complex carbohydrate and blend or set ofmicroorganisms provided in the remediation composition to degrade orbreak up the complex carbohydrate into smaller molecules to be utilizedmore effectively and over time (e.g., 20 to 365 days or more) by theblend or set of organisms provided for assisting the supported reactantin degrading the halogenated hydrocarbons. Further, the material is easyto use and does not require any special safety controls or equipment forinstallation.

The remediation composition and its use in remediating contaminatedsoil/groundwater is further illustrated by the following non-limitingexamples. All scientific and technical terms have the meanings asunderstood by one with ordinary skill in the art. The specific exampleswhich follow illustrate the methods in which the compositions of thepresent description may be prepared and are not to be construed aslimiting the invention in sphere or scope. The methods may be adapted tovariation in order to produce compositions embraced by this descriptionbut not specifically disclosed. Further, variations of the methods toproduce and use the same compositions in somewhat different fashion willbe evident to one skilled in the art.

Example 1 Preparation of a Supported Reactant by Low TemperatureDecomposition of Metal Nitrates

A measured amount of activated carbon is mixed with an associated amountof hydrated ferric nitrate calculated to provide the desired weightpercentage of elemental iron in the final product, e.g., 1 to 20 percentby weight iron. The iron salt is typically moist and on warming easilymelts, so that a uniform mixture results. As the mixture is stirred, itis warmed to roughly 50° C. to melt the salt. If necessary, a smallamount of water may be added to produce a mixture having a creamyconsistency. The mixture is then dried at a temperature of from 90 to110° C. so that the mixture can be crushed to a free flowing granularpowder. Some decomposition of the nitrate salt occurs during thisprocess.

The dried powder is then loaded into a furnace and heated in accordancewith a temperature program while maintaining reducing conditionsthroughout. Initially, the temperature is slowly raised to 150 to 200°C. to completely dry the reactant and continue degradation of the ironnitrate. The temperature continues to increase, and, at 300° C., thenitrate salt is completely decomposed into oxide.

Once the nitrate is completely degraded into oxide, a reducing gas suchas methane gas or hydrogen gas is introduced into the furnace atmosphereand the temperature is raised to from 550 to 850° C., completelyreducing the oxide to elemental iron. Note, the temperatures often aresignificant as the inventor has found that if the temperature is too lowas the iron is formed the iron does not dissolve into the carbon, and,as a result of this failure to dissolve into the carbon, one of the mostimportant features of the iron impregnated carbon may not be realized.Methane gas is safer to use than hydrogen and, therefore, is preferredin some implementations. The theoretical amount of water is typicallyformed upon complete reduction of the oxide as the temperature rises tobetween 400 and 450° C. when 100% hydrogen or methane is used.

Final properties of the supported reactant are influenced by theultimate reducing temperature. For example, when the reactant is reducedat temperatures below 700° C. and then exposed to the air after cooling,an exothermic reaction may occur, oxidizing a portion of the reducediron. However, when the final reduction is carried out at a hightemperature, for example between about 700 and 850° C., the reactant isstable and exposure to the air has no effect. If reduction is completedat a temperature of less than 450° C., the material can be pyrophoric.At reduction temperatures between about 450 and 700° C., variousreactant activities can be obtained.

Example 2 Preparation of a Supported Reactant by a PrecipitationProcedure

An appropriate amount of hydrated iron sulfate is dissolved in deionizedwater in a tank with stirring, and a measured amount of activated carbonis added. Stirring is continued after the addition is complete, and avacuum is applied to the tank to de-aerate the carbon. Once the carbonis de-aerated, a sufficient amount of a dilute solution of sodiumbicarbonate is slowly added to initiate precipitation of goethite andother iron oxides onto the suspended carbon. Pressurizing the tankduring addition of the bicarbonate can enhance the impregnation process.After the addition of bicarbonate is completed, mixing is continued forseveral more hours. The process is complete when testing of an aliquotfor ferrous iron is negative. The slurry is then washed with deionizedwater and filtered several times. Finally, the collected reactant isdried at 110° C. At this point, the carbon is impregnated with ironoxides and is ready for reduction.

The dried powder is loaded into a furnace and heated in accordance witha temperature program while maintaining reducing conditions throughout.Initially, the temperature is slowly raised to 150 to 200° C. tocompletely dry the reactant and continue degradation of the iron oxideand iron hydroxide. A reducing gas such as methane gas or hydrogen gasis introduced into the furnace atmosphere, and the temperature is raisedto from 550 to 850° C., completely reducing the oxide to elemental iron.Again, it should be remembered that the higher reduction temperatures(e.g., 800 to 850° C.) have been proven by the inventor to provide thedesired dissolving of the iron into the carbon, which is a highly usefulfeature of the impregnated carbon and may not be achieved at lowerreduction temperatures. Methane gas is generally safer to use thanhydrogen and therefore is preferred in some implementations. Thetheoretical amount of water is typically formed upon complete reductionof the oxide as the temperature rises to between 400 and 450° C. when100% hydrogen or methane is used.

Example 3 Application of a Composition to Remediate Soil/Groundwater

Small diameter (e.g., about 0.75 to 2 inches in diameter) injection rodsare driven to targeted depths (e.g., 5-150 feet). The depth will dependon the power of the drill rig and the hardness of the soil.Hydraulically powered direct-push drill rigs are used to pound/push theinjection rod to the desired depths, and then withdraw it about 6 inchesto open up a small void below the injection point. A premixed aqueoussuspension of a remediation composition with a supported reactant ofthis description is then injected under pressure down the rod. Pressureis allowed to build in the formation, and a slurry begins to flow outinto the formation. No attempt is made to control the path of fluidflow, but, rather, the objective is to achieve a substantiallyhomogeneous distribution of the suspension within the formation. Thesuspension tends to emanate outward in all directions from the base ofthe injection, and the average or effective radius of influence iscontrolled by the amount of fluid pumped into the rod.

After injection of the first batch of the suspension, a second (fresh)batch of the suspension can be prepared, a new injection rod installed,and the process repeated. Treatment in this fashion is continuedthroughout the plume, reducing concentrations of contaminants in thegroundwater concentrations as treatment progresses. If one could view across-section of the formation, the treatment regime is intended tocreate a three-dimensional network of material, dispersed randomly andfairly uniformly throughout the treated formation.

Many treatment technologies, ZVI for example, only work well wheninstalled in groundwater (saturated soils) and is not effective fortreatment of vadose zone (unsaturated) soils. Because activated carbonis very effective at adsorbing organic compounds from vapor streams, theremediation compositions of this description are able to perform nearlyas well when installed in the vadose zone. As a result, the remediationcomposition can be used equally well for treatment of contaminated soilsand groundwater.

With this understanding of the elemental iron-based composition and theuse of a remediation composition in mind, it may be appropriate at thispoint in the description to turn to formulas or recipes for the newremediation composition that builds upon the elemental iron-basedcomposition (e.g., activated carbon with iron impregnated in its pores).Particularly, the inventor experimented with a variety of remediationcompositions that include the elemental iron-based composition as partof the substrate for enhancing degradation of halogenated hydrocarbonsby bioremediation compositions chosen for this specific purpose. Thisenhanced performance is achieved, it is believed, by a combination ofcapturing or absorbing the contaminants in the pores of the activatedcarbon near the elemental iron (e.g., zero valent iron particles) andthen providing a hydrogen or electron source (or “fuel” source) for thebioremediation compositions that can be consumed over a longer period oftime than prior substrates.

The new remediation composition can generally be thought of as includingthe following main ingredients or materials: (1) a first set or blend ofone or more organisms (or a first bioremediation composition) thatfunctions to degrade halogenated compounds (e.g., chlorinated solventsand the like); (2) an elemental iron-based composition (such as thesupported reactant described above); (3) an organic compound orpolymeric substance (such as one or more polyamides and/orpolysaccharides (e.g., one or more complex carbohydrates); and (4) asecond set or blend of one or more organisms (or a second bioremediationcomposition) that functions to degrade the organic compound or polymericsubstance. Ingredients (2) to (4) may be considered a new composition orplatform (or act together to form a new platform) to facilitatebioremediation functionality of the first set or blend of one-to-manyorganisms.

As background to the origin of the remediation composition, it is usefulto understand that the inventor was considering the use of the elementaliron-based composition at sites contaminated with a broad mixture ofcontaminants. In one example (of many tests completed over years), thesite's groundwater was known to contain alcohols, aromatics, ketones,chlorinated solvents, ethers, and aliphatic compounds. The challenge inremediating such a site is that no single known technology can addressall the contaminants of concern. Testing of this exemplary showed thattotal contamination of the groundwater was roughly 2,000 ppm or 0.2%(wt) of toxic organic compounds.

As a consequence of this range of contaminants and the propensity forgeneration of recalcitrant daughter products, most remedial strategies(prior to the new remediation composition) would likely include the useof multiple techniques implemented in series over a period of time. Eachtechnology in this series would be designed to target a very specificset of contaminants and would be used or run to its conclusion beforethe next technology targeting different contaminants would be employedat the site. With these issues in mind, the inventor discovered acombination of technologies (i.e., a new remediation composition aslabeled herein) that would work together in a new and improved manner soas to provide one treatment that can be used on sites like the exampleprovided above to achieve targeted cleanup levels. The use of just asingle remediation composition is highly desirable—but not in existenceprior to the new remediation composition—as it would provide asubstantial reduction in time, cost, and the field effort. As willbecome clear, the discovered remediation compositions taught herein maybe utilized (such as in the method discussed in Example 3) in the fieldto successfully remediate a contaminated site (e.g., a site withcontaminants including halogenated compounds).

Trace metals were added to each test bottle of groundwater from thecontaminated site along with the other ingredients of the remediationcompositions. During an active remediation, though, there is typicallyno need to include trace metals to maintain good microbial growth asthese are available from minerals in the subsurface and in groundwater.However, when only groundwater is utilized, some trace metals areneeded. Also, micro and macro nutrients were added to the test vials orbottles to help create a very favorable environment for cell growth, butthese nutrients typically are readily available in contaminated soilsand groundwater and do not generally need to be included in aremediation composition.

With regard to useful and desirable ingredients for the new remediationcomposition, the first ingredient is a set or blend of one or moreorganisms chosen specifically to degrade the targeted contaminants. Inthis case, the targeted contaminants are halogenated compounds includingchlorinated solvents and the like. The inventor used a remediationcomposition that included three differing sets or blends of suchmicroorganisms, and the results showed that it is highly likely that awide variety of sets/blends will be useful in remediation compositionwhen combined with the other three ingredients in effectively degradinghalogenated compounds. One set or blend of one or more microorganismswas commercially available (e.g., from vendors as a liquid concentrate)and was a blend of many organisms that in the past had been demonstratedto degrade fuel hydrocarbons such as benzene, toluene, xylenes, and thelike. The second tested set or blend of microorganisms was a blend oforganisms (again, commercially available as a liquid concentrate) thathas proven (or is known) to be able to degrade chlorinated solvents andother halogenated compounds including chloroform cis-DCE(dichloroethylene), methylene chloride, TCE (trichloroethylene), VC(vinyl chloride), and chlorobenzene. The third tested set or blend ofmicroorganisms was a blend of dehalococcoides (DHC) that is alsocommercially available (e.g., distributed by SiREM of Canada as KB-1®)and is designed to degrade various chlorinated compounds completely tohydrocarbon gases. Note, this first “ingredient” may include two or morevendor-provided compositions that are combined to degrade all thetargeted contaminants of a particular site.

The second ingredient in the “recipe” for the bioremediation compositionprovided above is an elemental iron-based composition such as oneincluding activated carbon and elemental iron. In some preferredembodiments, this elemental iron-based composition takes the form of oneof the supported reactants described herein and which can bemanufactured as described above so as to provide activated carbon withiron impregnated in its many pores. Such a supported reactant iseffective for absorbing contaminants such as halogenated compoundswithin the pores near the elemental iron particles.

The third ingredient used in the making of the bioremediationcomposition is an organic compound or polymeric substance (such as acomplex carbohydrate or other polysaccharide and/or a polyamide) whilethe fourth ingredient is a second set or blend of microorganisms, whichis selected due to their ability to degrade the organic compound orpolymeric substance (e.g., degrade particular complex carbohydrate suchas a food grade starch). In one useful embodiment, this second set orblend of microorganisms in the tests was known to be able to degradecomplex carbohydrates such as cellulose and starch to smaller compoundsthat can then be beneficially used by other organisms (e.g., those ofthe first set or blend in the remediation composition) to degrade sitecontaminants (e.g., halogenated compounds such as chlorinated solvents).When other organic compounds or polymeric substances are used, it may bedesirable to choose the second set or blend of one or moremicroorganisms for its ability to degrade that organic compound(s) orpolymeric substance(s). These two ingredients (or the elementaliron-based composition may also be included) may be thought of asproviding a time release substrate for fueling degrading processes bythe first set or blend of the microorganisms at a site.

In performing the bench tests, the inventor performed testing with aplatform (or composition) in the form of lactic acid (in the form ofsodium lactate but without a second blend of organisms used to degradethe lactate). Lactate is commonly used for bioremediation of chlorinatedsolvents in combination with blends of DHCs and other organismseffective at degradation of such compounds. These tests showed orverified that a significant limitation of lactate as a platform is thatit is water soluble such that it tends to move with groundwater and israpidly consumed such that it is ineffective for supporting degradationover longer periods of time (e.g., is not a “time release substrate”).As a result, in practice, remediation of sites with lactate as aplatform require that a number of supplemental doses of lactate beapplied to maintain a persistent concentration supportive of thedegradation pathways. This undesirably adds to the cost and field workefforts of the remediation of a contaminated site.

In the bench tests, the inventor determined that it would be highlyuseful and desirable for the third and fourth ingredients of theremediation composition to be chosen to provide materials that could bebeneficially used and consumed by the one or more microorganisms over anextended time period (e.g., 20 to 365 days or longer). Particularly, itwas determined that organic compounds in the form of complexcarbohydrates (e.g., food grade starch or chitin) are readily availableand inexpensive and may provide the characteristics of a material usefulin the substrate. It was recognized that, in contrast to lactate, manycomplex carbohydrates have low water solubility so that they are lesslikely to move with the groundwater than lactate. Further, the inventorrecognized that the complex carbohydrates could be degraded or brokendown over an extended period of time to provide a time release platformor composition for facilitating or supporting (during remediationprocesses) the first set or blend of organisms in the remediationcomposition.

Specifically, it was understood by the inventor that starch (e.g., acarbohydrate (or a polysaccharide) has a large number of glucose unitsjoined by glycosidic bonds, and it may include two types of molecules inthe form of linear and helical amylose and branched amylopectin, whichmay be provided in the form of food grade starch, may have low watersolubility and may be easily degraded by a wide variety of organisms,which can be provided as the fourth ingredient of the remediationcomposition. Similarly, chitin (e.g., another natural polysaccharide)was identified by the inventor as another potential material for theremediation composition as it has low water solubility and has proven tobe a useful platform or composition for degradation of chlorinatedsolvents using one or more microorganisms.

Both the starch and chitin were believed to have the potential to be“time release” sources of smaller molecules that can be utilized by themicroorganisms (of the first set or blend) to more effectively performdegradation (e.g., degradation of chlorinated organic compounds (COCs)over time without a need for addition of more substrate materials). Thispotential was shown in the bench test in which starch or chitin (thethird ingredient of the remediation composition) was used along with asecond blend or set of one or more organisms chosen for their ability todegrade complex biopolymers (such as the complex carbohydrates ofstarch, chitin, and the like) to provide a time releasing mechanism forthe smaller molecules/compounds used as “fuel” for degradation processesby the organisms of the first set or blend of one or more organisms inthe remediation composition.

In the tests, the remediation composition was added to bottles of theground water as follows: (1) 1.0 or 1.5 ml quantities of the first setor blend of one or more organisms (or more if two or more liquidconcentrates from vendors was used to target different contaminants);(2) 1.5 or 2.0 grams nominal of the elemental iron-based composition;(3) 0.5 grams of the complex carbohydrate (e.g., starch, chitin, or thelike); and (4) 1.0 or 1.5 ml quantities of the second set or blend oforganisms. It is believed that the “starter” amount used for the firstand second sets of organisms can be varied widely to practice theremediation composition as these will grow over time in use at a site.The ratio of the elemental iron-based composition to the complexcarbohydrate may also be varied to provide a useful remediationcomposition with the given ratio of at least 1 to 2 being one usefulexample (e.g., with ratios of 1:1, 1:3, 1:4, and the like alsoconsidered within the breadth of this description). In brief, the benchtesting verified that the remediation composition was effective over anextended period of time in degrading the halogenated compounds (e.g., indegrading the COCs to target levels).

In one implementation, the elemental iron-based composition used in theremediation composition was a granular activated carbon whose inner porestructure had been impregnated with elemental iron. The elementaliron-based composition was not simply a mixture of activated carbon andpowdered iron, and it is inaccurate to even think of it as beingactivated carbon with bits of zero valent iron (ZVI) present within thepore structure. Instead, as discussed above, the manufacturing processfor this key ingredient of the remediation composition may, in somepreferred embodiments, begins with granular activated carbon (GAC) andimpregnates this feedstock carbon with an aqueous solution of an ironsalt. The intermediate product is then processed at higher temperatures(e.g., at or above 850° C.) under reducing conditions in a rotaryfurnace. Under these conditions, the iron salt decomposes, and elementaliron is formed. As it is formed, it partially dissolves into the carbon.

Significantly, the transition between the carbon and the metallic ironshows the presence of cast iron and iron carbide. This physicalconnection results in an interaction that activates the iron allowing itto perform in ways that ZVI and nano-scale iron powders alone cannot.One example of this is the ability of this elemental iron-basedcomposition (or supported reactant) to degrade carbon tetrachloride andchloroform completely without generation of methylene chloride and alsoto degrade vinyl chloride. Further, this form of the elementaliron-based composition degrades halogenated compounds abioticallythrough chemical reduction.

With the above discussion in mind, it may now be useful to describe anumber of useful aspects or characteristics of the supported catalyst(e.g., the elemental iron-based composition). The supported catalystoften will include coal-based activated carbon. Other materials can beused, but the final properties of the supported catalyst are highlydependent on the starting material. Bituminous coal-based carbons havebeen proven by the inventor to meet all adsorbent requirements detailedin this description. In one preferred embodiment, the carbon isactivated in steam and carbon dioxide at approximately 1000° K for about30 to 60 minutes. This supported catalyst has a carbon surface area inthe range of 800 to 1800 m²/gm. The activated carbon is capable ofadsorption of halogenated organic compounds from vapor and liquidstreams. The activated carbon is also preferably capable of adsorptionof toxic intermediates arising from reaction of metallic iron withprimary halogenated organic compounds (contaminants). The supportedcatalyst is fabricated or manufactured in many cases to have a metalliciron surface area in the range of 50 to 400 m²/gm iron. The loading ofmetallic iron is typically between 1 to 20% (wt). In practice, themetallic iron formed is preferably free of surface oxides or othercoatings.

The reduction temperature used to produce the supported catalyst is 973to 1200° K, with some embodiments using a reduction temperature of about1140° K. This high temperature reduction is useful to develop thedesired contact between the active carbon surface and the sub-microndeposits of metallic iron. It is also important in some applications todevelop insensitivity to air exposure, which prevents creation of anoxide film that would result in the product becoming completely useless.At the higher reduction temperature, Mossbauer Spec data shows that asthe salt is reduced and metallic iron is formed, the metal partiallydissolves into the carbon. Carbon grading to cast iron and iron carbidegrading to elemental iron in a couple of different crystal forms can beobserved. As a consequence, there is an interaction between the carbonand the metal that creates unique properties that commercial ZVI doesnot have. Because of this interaction, the metallic iron is stable incontact with groundwater (GW) and can remain active for an extendedtime. Data has been collected showing activity beyond 8 years when incontact with water and the presence of trace dissolved oxygen has notmattered. This is important because iron powder and nano-scale ZVI inparticular do not remain active in contact with groundwater for extendedperiods. In addition, the supported catalyst can degrade compounds thatZVI cannot or is very poor at. For example, the supported catalyst candegrade carbon tetrachloride and chloroform rapidly without significantgeneration of methylene chloride. It can readily degrade vinyl chlorideand is effective with compounds like 1,1-DCA and 1,2-DCA.

It should also be understood, though, that there are a number oflimitations to use of this supported catalyst. Reaction of the metalliciron embedded within the pore structure with halogenated organiccompounds consumes the iron. This is referred to as the “iron demand”and is dependent on the specific compound. For example, the iron demandfor carbon tetrachloride is substantially higher than that for vinylchloride. Because the metallic iron is depleted and there are limits tothe weight percent of iron that can realistically be loaded within thepore structure of the carbon, this results in an upper constraint on theamount or mass of the halogenated compound that can be degraded by aunit weight of impregnated carbon. As a result, when the soilconcentrations of various halogenated compounds exceed approximately1,000 ppm, the cost for treatment becomes high and treatment of DNAPLcan be significant. Additionally, some compounds, such as chlorobenzenesand fluorinated compounds (e.g., fire retardants and perfluorooctanoicacid (PFOA)), are resistant to degradation by this material.

To understand the desirability and usefulness of the presently describedcompositions, it may now be useful to more fully discuss biologicaldegradation of halogenated compounds. In general, whenever you have thefollowing conditions: Microorganisms+electron donors+electronacceptors+nutrients, biological activity will occur that can potentiallydegrade contaminants and promote growth. There are many reactions thatcan occur, but they can be grouped into the following classifications:(a) use of the organic compound as a primary growth substrate; (b)growth promoting biological oxidation; (c) growth promoting biologicalreduction; (d) fermentation; and (e) cometabolism.

The first group classification or group includes pathways such asreductive dehalogenation and halorespiration. Fermentation is animportant mechanism as this is one of the primary means for generationof hydrogen which is an important electron donor and takes part innumerous pathways resulting in replacement of hydrogen for chlorine onthese halogenated compounds. In this process, chlorine atoms aredisplaced by hydrogen forming a host of daughter products. Commonpathways shown in the literature for degradation of say TCE into a hostof less chlorinated compounds like DCEs and VC are typically throughreductive dechlorination. Fermentation may have a number of indicators.For example, generation of methane is strong evidence that fermentationis occurring as is generation of fatty acids. Aside from hydrogen andmethane, a variety of fatty acids are produced by fermentation includingacetate, formate, lactate, succinate, propionate, and butyrate. Oncefatty acids are present, secondary fermentation may commence thatconsumes C3 and higher acids to yield additional acetate, formate,water, and hydrogen.

Cometabolism is a process by which the halogenated contaminant isdegraded through enzymes and cofactors employed by the organism formetabolism of some other primary substrate (electron donor). Lactate iscommonly used in this way for bioremediation of chlorinated solvents inconcert with DHC and other organisms effective at degradation of suchcompounds. Many other materials have been employed for this purposeranging from agricultural waste like corn cobs to crab and shrimp shells(chitin) to polymers like polylactates. Chitin is a material essentiallyinsoluble in water but has been shown to be an effective platform orcomposition for degradation of chlorinated solvents using one or moremicroorganisms.

There are several key features of bioremediation. Naturally occurringmicroorganisms are typically able to degrade a wide spectrum ofcontaminants. In many cases, metabolic byproducts are also toxiccontaminants; however, these compounds are also susceptible tobiodegradation. For the most part, microorganisms are fairly robustbeing able to thrive in a wide range of conditions including pH,temperature, and salinity (but, note, there are exceptions to thisrule). Essential nutrients such as trace metals are often available fromthe mineral content of subsurface soils. Alternative platforms orcompositions are often advantageous and are widely used to promote thedegradation of contaminants of concern. One common platform orcomposition used for this purpose is lactic acid.

There are, however, a number of limitations of bioremediation.Microorganisms often are unable to completely transform toxiccontaminants into harmless byproducts. For example, some highly usefulorganisms convert TCE into vinyl chloride but are not able to degradethe vinyl chloride. As a result, other means are needed to deal with thevinyl chloride. One limitation of lactate is that it is water solublesuch that it tends to move with groundwater and is rapidly consumed. Asa result, supplemental doses of lactate are typically applied inpractice to maintain a persistent concentration supportive of thedegradation pathways. Other platforms or compositions such as vegetableoil or emulsified oils ferment slowly, and a high percentage of thisactivity is not beneficially captured to degrade targeted contaminants.Some organisms are difficult to handle and sensitive to subsurfaceconditions such as pH. Since contaminants are typically used as electrondonors by the organisms (food source), as contaminant concentrationsfall the microbial populations fall off and remedial progress stalls.

With all this in mind, the inventor has designed and fabricated acomposition that is effective in combining biological degradation ofhalogenated compounds with an absorbent impregnated with metallic iron.It should be understood that the product (supported catalyst orelemental iron-based composition as labeled herein) made by impregnatingthe inner pore structure of activated carbon with metallic iron is veryeffective at degrading many halogenated compounds. Further, the rate ofdegradation of these compounds is very rapid. The activated carbonconcentrates the contaminants, which enables effective contact with avery active and large metallic surface area. Nearly all of theabsorption of organic compounds by the carbon will be within themicro-porous structure. Microorganisms will tend to inhabit the macroand meso-pore structure of the carbon as they are too large for accessto the micro-pores.

The active metallic iron also resides within the micro-pores and so itwould be expected that absorbed contaminants will rapidly react with theiron and very little biological degradation would be possible since themicrobes are limited to the larger pores. If this were the case, thenhalogenated compounds would simply react with the available iron untilit is depleted and residual contaminant residing within the micro-poreswill slowly desorb over time. Such a process would severely limit thebiological degradation rendering it nearly ineffective. Two essentialfeatures are missing from the above discussion. First is the fact thatcarbon and iron are conductors, and there is an additional interactionbetween them due to the iron partially dissolving into the carbon. Themetabolic (biological process) process involves both electron donors andacceptors. Thus, there is a transfer of electrons during degradation orrespiration of these halogenated compounds and the carbon and iron canfacilitate this process. Recent work has shown that activated carbon caneffectively shuttle electrons to absorbed compounds. The ironimpregnated carbon will provide an even more effective platform for theshuttling of electrons.

The second missing feature has to do with whether absorbed compounds arebioavailable. In other words, it must be determined whethermicroorganisms residing within the macro and meso-pore structure of thecarbon affect compounds stored within the microporous structure.Research performed by the inventor has produced definitive data provingthat compounds absorbed by activated carbon are degraded bymicroorganisms residing in the larger pore network. When these twofeatures are combined, the result is a highly effective and efficientsystem for degradation of halogenated compounds. Microorganisms secretecofactors and enzymes that are able to penetrate into the microporousstructure of the carbon and the metallic iron/carbon platform providesthe shuttle for transport of electrons to complete the reaction. In thisprocess, the iron is not consumed as it is if abiotic dechlorinationreactions are in play. The net effect of this is that the rapiddepletion of metallic iron within the pore structure of the carbon doesnot occur because of the electron shuttle created to fuel the biologicaldegradation of absorbed compounds. There is, in effect, a very efficientsystem to catalyze the biological degradation pathways over depletion ofthe metallic iron.

The inventor then understood that the last piece of the puzzle has to dowith providing an effective time release mechanism or platform togenerate suitable fuels to support this process over time. Currently,materials that stem from low molecular weight fatty acids such as lacticacid or emulsified oils are utilized to facilitate bioremediation.However, neither of these or other materials in common use are wellsuited to support degradation over an extended period of time in anefficient manner. Simple addition of a complex carbohydrate or otherorganic compound is not enough as those microorganisms adept atdegrading halogenated compounds are not typically suited to thebreakdown or fermentation of such materials. As a result, the process isslow at best and, in many cases, nonexistent.

The key identified by the inventor is to add one or more organisms whosemain function is degradation of organic compounds or polymericsubstances (e.g., complex carbohydrates such as starch and cellulosicmaterials). When this is done, the organic compounds or polymericsubstances (e.g., complex carbohydrates such as food grade starch) beginto function as time release platforms (or fuel supplied) or compositionsbecause the large molecules are broken down into small pieces that arenow directly usable for beneficial degradation of halogenated compounds.Although chitin was shown to perform in this system, it is virtuallyinsoluble in water, and its structure is very much like cellulose.Cellulose is difficult to breakdown and was recently the focus of thebiofuels industry and a concerted effort was put into fermenting thisabundant material into ethanol. This proved to be more difficult thanenvisioned and chemical rather than biological means have beencommercialized for production. The search for acceptable microorganismscontinues and one of the more promising avenues involves looking fororganisms in the feces of animals that eat cellulose such as the pandawho survives mainly by consuming bamboo. Another limitation of chitin isthat it is a byproduct of the fishing industry, being made from crab andshrimp shells. Fishing for these creatures is a seasonal activity and sothe availability of chitin is not necessarily always dependable.

Among the many organic compounds tested, starch (e.g., corn or potatostarch or other food grade starch) produced the best overall results.Food grade starch is readily available and inexpensive. Starch isslightly soluble in water and is readily fermented by a range ofnon-pathogenic organisms. For these reasons, starch is one preferredpolysaccharide (or organic compound or polymeric substance) for use inthe described system or as part of a platform for bioremediationorganisms. In general, many other complex carbohydrates may be used, andthe complex carbohydrate may be a polymer with a formula ofC_(m)((H₂O)_(n)), wherein m and n are different integers and wherein mis greater than 6 such as greater than 12. Starch-containing materialssuch as corn cobs and potatoes may be utilized. However, all of these“starch containing” materials suffer from the fact that they consistprimarily of cellulosic material and suffer from the associatedlimitations thereof. For purposes of this invention, such materialscould be used; however, they likely will not be as effective as foodgrade starch. For example, in one test, measurement of chloridedemonstrated that the ratio of biological to chemical (abiotic)degradation was approximately 1.3:1. Further research may be useful tofurther increase this ratio and extend the life expectancy of theimpregnated iron. It is expected that this system can be applied to awide range of site conditions and was specifically developed to targetsource area impacts. Further, although not considered examples ofcomplex carbohydrates, oligosaccharides (such as raffinose andstachyose, which are found in beans, cabbage, and the like) may be usedalong with or, in some cases, in place of one or more complexcarbohydrates.

Representative examples of organisms (or microorganisms that may be usedto provide a first bioremediation material as called out in thefollowing claims) that degrade halogenated compounds fall into severalmetabolic groups including (but not limited to): halorespirators;acetogens; methanogens; and facultative anaerobes. Examples ofhalorespirators include Dehalococcoides strains (SiRem of Canada offersa consortia of these called KB-1), Dehalobacter restrictus, andDeesulfitobacterium dehalogenans. Examples of acetogens includeClostridium aceticum and Bacillus acetogens. Examples of methanogensinclude Methanobacterium bryantii, Methanococcus deltae, Methanogeniumcariaci, and Methanosarcina acetivorans. Also, many methanogens arefound among the Archea (e.g., there are over 50 described species).Examples of facultative anaerobes include bacterial and fungal generasuch as Actinomyces, Bacteroides, Clostridium, Porphyromonas, andVeillonella species. Of course, one skilled in the art will readilyunderstand that the above examples are a few of many microorganisms thatare known and may be included singly or in combination in the firstbioremediation material.

As discussed above, there are many types of starch (or food gradestarch) with sources such as potato, corn, maize, rice, tapioca, wheat,soybean, and plants (or plant products). Likewise, a variety oforganisms may be used alone or in combination in the secondbioremediation material (as called out in the claims) to provide usefuldegradation of such starches. Two common breakdown products of thebiological degradation of starch are maltose and glucose. Examples ofbacteria that may be provided in the second bioremediation materialinclude: Bacillus amyloliquefacicns, Bacillus licheniformis, Bacillussubtilis, and Pseudomonas spp. Further, examples of fungi that may beprovided in the second bioremediation material include: Aspergillusniger and Penicillium.

The foregoing description is considered as illustrative only of theprinciples of the compositions and methods described and later claimed.The words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of one or more stated features,integers, components, or steps, but they do not preclude the presence oraddition of one or more other features, integers, components, steps, orgroups thereof. Furthermore, since a number of modifications and changeswill readily occur to those skilled in the art, it is not desired tolimit the invention to the exact construction and process showndescribed above. Accordingly, all suitable modifications and equivalentsmay be resorted to falling within the scope of the invention as definedby the claims that follow.

For example, one preferred implementation provides a remediationcomposition with an adsorbent impregnated with a reducing agent foradsorbing at least one halogenated compound. The term “reducing agent”is intended to include all metals, alloys, and a range of othermaterials at provide reducing functionality such as, but not limited to,one or more sulfides. Further, the composition includes a first set ofone or more microorganisms able to degrade the at least one halogenatedcompound. To provide a time release quality, the composition includes atleast one polyamide or at least one polysaccharide, or a polypeptide(with polypeptides likely being useful as a substitute for starch or asa supplemental material to create time release of nitrogen, which can bevital for cell growth) and a second set of one or more microorganismsbreaking the at least one polyamide, at least one polysaccharide, or atleast one polypeptide into smaller molecules or compounds useful to thefirst set of one or more microorganisms during degradation of thehalogenated compound. Note, the composition may include a combination ofone or more polyamides, polysaccharides, and polypeptides (e.g., with“or” meaning at least one of these three materials but could contain twoof the materials or all three of the materials).

The second set of or more microorganisms (e.g., algae, fungi, bacteria,archaea, or one or more unicellular organisms) degrades the at least onepolyamide, at least one polysaccharide, or at least one polypeptide overa period of time. Further, the smaller molecules or compounds donateelectrons for use by the first set of one or more microorganisms duringthe degradation of the set of halogenated compounds, whereby incombination the at least one polyamide, at least one polysaccharide, orat least one polypeptide and the second set of one or moremicroorganisms provide a time release platform fueling the degradationby the first set of one or more microorganisms. In some embodiments, theadsorbent is activated carbon and the reducing agent is an alloy, asulfide, and/or a metal. In particular cases, the reducing agent is ametal, such as elemental iron, that is impregnated into the activatedcarbon by being at least partially dissolved into walls of pores of theactivated carbon. Then, transitions in the walls of the pores betweenthe activated carbon and the elemental iron may be cast iron and ironcarbide.

The composition may be formed to have a time-release period greater than20 days. The at least one polyamide, at least one polysaccharide, or atleast one polypeptide may take the form of food grade starch or chitin(or a combination thereof). In other cases, though, the at least onepolyamide, at least one polysaccharide, or at least one polypeptide ismade up of shredded wool or feathers (or both).

I claim:
 1. A remediation composition, comprising: an adsorbent foradsorbing at least one halogenated compound, wherein the adsorbent isimpregnated with a metal; a first set of one or more microorganisms ableto degrade at least one halogenated compound, wherein the first set ofone or more microorganisms includes acetogens; and a time releasecompound, combined with the first set of one or more microorganisms,comprising: a polymeric substance comprising at least one of apolyamide, a polypeptide, and a polysaccharide; and a second set of oneor more microorganisms mixed with the polymeric sub stance, wherein thesecond set of one or more microorganisms degrades, over a period oftime, the polymeric substance into smaller molecules or compounds thatdonate electrons for use by the first set of one or more microorganismsduring degradation of the halogenated compound and wherein the period oftime has a length of at least 20 days.
 2. The composition of claim 1,wherein the second set of one or more microorganisms includes bacteriaincluding at least one of Bacillus amyloliquefacicns, Bacilluslicheniformis, Bacillus subtilis, or Pseudomonas spp.
 3. The compositionof claim 1, wherein the second set of one or more microorganismsincludes fungi.
 4. The composition of claim 3, wherein the fungicomprises at least one of Aspergillus niger and Penicillium.
 5. Thecomposition of claim 1, wherein the second set of one or moremicroorganisms comprises algae.
 6. The composition of claim 1, whereinthe adsorbent comprises activated carbon and the metal compriseselemental iron.
 7. The composition of claim 6, wherein the elementaliron is impregnated into the activated carbon by being at leastpartially dissolved into walls of pores of the activated carbon andwherein transitions in the walls of the pores between the activatedcarbon and the elemental iron comprises cast iron and iron carbide.
 8. Aremediation composition, comprising: an adsorbent for adsorbing at leastone halogenated compound, wherein the adsorbent is impregnated with ametal; a first set of one or more microorganisms able to degrade atleast one halogenated compound, wherein the first set of one or moremicroorganisms includes methanogens; and a time release compound,combined with the first set of one or more microorganisms, comprising: apolymeric substance comprising at least one of a polyamide, apolypeptide, and a polysaccharide; and a second set of one or moremicroorganisms mixed with the polymeric sub stance, wherein the secondset of one or more microorganisms degrades, over a period of time, thepolymeric substance into smaller molecules or compounds that donateelectrons for use by the first set of one or more microorganisms duringdegradation of the halogenated compound and wherein the period of timehas a length of at least 20 days.
 9. The composition of claim 8, whereinthe second set of one or more microorganisms includes bacteria includingat least one of Bacillus amyloliquefacicns, Bacillus licheniformis,Bacillus subtilis, or Pseudomonas spp.
 10. The composition of claim 8,wherein the second set of one or more microorganisms includes fungi. 11.The composition of claim 10, wherein the fungi comprises at least one ofAspergillus niger and Penicillium.
 12. The composition of claim 8,wherein the second set of one or more microorganisms comprises algae.13. The composition of claim 8, wherein the adsorbent comprisesactivated carbon and the metal comprises elemental iron.
 14. Thecomposition of claim 13, wherein the elemental iron is impregnated intothe activated carbon by being at least partially dissolved into walls ofpores of the activated carbon and wherein transitions in the walls ofthe pores between the activated carbon and the elemental iron comprisescast iron and iron carbide.
 15. A remediation composition, comprising:an adsorbent for adsorbing at least one halogenated compound, whereinthe adsorbent is impregnated with a metal; a first set of one or moremicroorganisms able to degrade at least one halogenated compound,wherein the first set of one or more microorganisms includes facultativeanaerobes; and a time release compound, combined with the first set ofone or more microorganisms, comprising: a polymeric substance comprisingat least one of a polyamide, a polypeptide, and a polysaccharide; and asecond set of one or more microorganisms mixed with the polymeric substance, wherein the second set of one or more microorganisms degrades,over a period of time, the polymeric substance into smaller molecules orcompounds that donate electrons for use by the first set of one or moremicroorganisms during degradation of the halogenated compound andwherein the period of time has a length of at least 20 days.
 16. Thecomposition of claim 15, wherein the second set of one or moremicroorganisms includes bacteria including at least one of Bacillusamyloliquefacicns, Bacillus licheniformis, Bacillus subtilis, orPseudomonas spp.
 17. The composition of claim 15, wherein the second setof one or more microorganisms includes fungi.
 18. The composition ofclaim 17, wherein the fungi comprises at least one of Aspergillus nigerand Penicillium.
 19. The composition of claim 15, wherein the second setof one or more microorganisms comprises algae.
 20. The composition ofclaim 15, wherein the adsorbent comprises activated carbon and the metalcomprises elemental iron.
 21. The composition of claim 20, wherein theelemental iron is impregnated into the activated carbon by being atleast partially dissolved into walls of pores of the activated carbonand wherein transitions in the walls of the pores between the activatedcarbon and the elemental iron comprises cast iron and iron carbide.